Vole Population Dynamics and Predatory Birds

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Vole Population Dynamics and Predatory Birds

• By Kurt Herrick

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Northern Voles

• This experiment was conducted in southeastern
  Norway, a vole hotspot for climate variability,
  dispers-ed population and of course, predators

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• Two field procedures, one on local demographic
  mechanisms and the landscape-depended annual
  synchrony on the 28 controlled populations while
  the other is a regional, multi-annual synchrony
  in open, uncontrolled habitats.

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• A population of 481 root voles were fixed with a
  radio transmitter to see if aviating predators
  was a synchronizing mechanism.

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• The vole predators had to be distinguished from
  each other as the attacks commenced because they
  each formulate from two different scales.

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• Seven of the root voles habitats were enclosed
  by 50X100 meter electric fences located in a
  meadow with an open ceiling for raptors and owls
  to strike their prey. The fence prevented any
  terrestrial predators from entering.

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• Over the breeding season, the voles had
  fluctuations in their population sizes. The
  fecundity levels did not differ in the years of
  1990 to 1994. The summer season had not been
  determined as an affect on vole dynamics except
  that the diet changes.

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• The predatory birds consisted of mainly owls and
  hawks and raptors. The owls hunt at night so the
  attempts of this research did not focus on them.

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• Instead, the voles were fitted with those
  transmitters to quantify the predation rates.

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• These small mammals were very susceptible to
  being captured while they moved across their
  constrained habitat. Across far more open areas
  lead the voles to be likely captured by avian
  predators. The frequencies of dispersal movements
  increased with decreasing vole densities.

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• It was reported that bird predation synchronized
  the vole population statistics at a focused and
  controlled scale, it was expecting that an
  increase in growth rates of the experimental
  populations to correlate with the focused vole
  abundance.

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• In a region of low prey density, the local
  hotspots are under jurisdiction of spatially
  density-dependent predation habits and equaling
  low growth rates.

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• Vole population statistics was sternly
  synchronized at two temporal scales. A
  within-year scale at a landscape perspective and
  a between-year synchrony at a regional overview
  to match rates of growing experimental
  populations with the regional tally.

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• The fecundity levels and body growth of the root
  voles did not change significantly during these
  tests.

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• Since summer seemed to be an off-time of the
  prime hunting on voles, the predation rates
  lowered enough to raise a sufficient amount of
  population synchrony. Instead, the decline, if
  any on voles are induced from ground predators
  like minks and weasels.

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Conclusion

• The study amplifies the unusual loop set between
  predation and prey relationships, strictly
  optioning on the vole dangerous methods of
  dispersal that ends up as an influence or
  provocation of predatory attack for a
  synchronizing effect either in a habitat or the
  more influential regional standards.

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